The present invention relates to a ball bearing assembly with a bearing ring guide type ball retainer. More particularly, this invention relates to a ball bearing assembly having a bearing ring guide type ball retainer with ball pockets shaped to optimize the amount of lubricant retained within the ball pockets.
Small diameter ball bearings are typically used in applications such as rotatably supporting a motor drive shaft in hard disk or floppy disk drives for conventional personal computers or word processors. Conventional small diameter ball bearings are often provided with molded plastic ball retainers, in which the ball retainers are either of the bearing ring guide type, or of the ball guide type. A bearing ring guide type ball retainer is guided by either the inner or outer races of the bearing, and a ball guide type ball retainer is guided primarily by the balls themselves. With either of the conventional ball retainers, it is common for the frictional torque of the bearing assembly during operation to gradually decrease from an initial relatively high value, until the frictional torque becomes substantially stabilized. The ball pockets for receiving each ball in a conventional ball retainer are illustrated in FIGS. 7-10. In FIGS. 7 and 8, a conventional bearing ring guide type ball retainer is illustrated, showing a conventional cylindrical inner wall for the ball pocket of the ball retainer. In FIGS. 9 and 10, a conventional ball guide type ball retainer is illustrated, showing a conventional spherical inner wall for the ball pocket. Lubrication problems commonly exist for ball bearing assemblies in which the balls are retained within the pockets of conventional ball retainers. For instance, with a conventional bearing ring guide type ball retainer having a cylindrical inner wall for each pocket, excessive lubricant often builds up within the ball pockets since the shape of the inner wall does not allow for the lubricant to be scraped off of the ball surfaces during operation.
With conventional ball guide type ball retainers, excessive lubricant adhering to a surface of a ball is scraped off at the edge portions of the spherical inner wall of each pocket. The excessive lubricant then adheres to the inner or outer peripheral wall surfaces of the ball guide type ball retainer without affecting torque. However, with conventional ball guide type ball retainers having ball pockets with spherical inner walls, fast rotation of the bearing assembly can result in too much lubricant being scraped from the ball surfaces, with the resultant generation of abnormal noise caused by improper lubrication.